In recent years, in the prevailing trend toward the application of a large electric current having higher frequencies to circuits of electrical and electronic equipment, not only the electrical and electronic equipment but also the magnetic element is required to follow the trend. But the characteristic of a ferrite material which presently prevails as the magnetic body has reached the limit. Consequently new magnetic materials are being searched for. For example, the ferrite material is being replaced with a compression molded magnetic material such as sendust and an amorphous material; and an amorphous foil band. But the compression molded magnetic material has a poor moldability and a low mechanical strength after the compression molded magnetic material is fired. The production cost of the amorphous foil band is high because it is produced through winding, cutting, and gap forming processes. For these reasons, practical applications of these magnetic materials have been delayed.
Aiming at providing a method of producing a magnetic core component which has a variety of configurations and characteristics, is compact, and is inexpensive by using magnetic powder having a low moldability, the present applicant proposed a method of producing the core component having a predetermined magnetic characteristic by performing injection molding. The core component is composed of the compression molded magnetic body or the compressed powder magnet molded body containing a binding agent having a melting point lower than the injection molding temperature thereof. In the core component production method, the magnetic powder contained in the resin composition to be injection-molded is coated with the insulation material and thereafter the compression molded magnetic body or the compressed powder magnet molded body is insert-molded in the above-described resin composition. The present applicant obtained a patent for this production method (patent document 1).
Aiming at providing the composite magnetic core which can be arbitrarily shaped by using magnetic powder having a low moldability and which has a magnetic characteristic excellent in its DC superimposition characteristic and providing the magnetic element composed of this composite magnetic core and the coil wound around the composite magnetic core, the present applicant filed a patent application for the composite magnetic core composed of the combined body of the compression molded magnetic body obtained by compression molding magnetic powder and the injection molded magnetic body obtained by injection molding the magnetic powder, whose surface has been electrically insulated, to which binding resin is added. The injection molded magnetic body is used as the housing in which the compression molded magnetic body is disposed (patent document 2).